[Amps] Subject: Henry hum on transmitted signal

David Gow 6146guy at gmail.com
Mon Sep 4 13:07:07 EDT 2023 

If the cap is bad Henry Radio still sells the resonating cap at their
on-line eBay store for $129.  The description says it is of current
manufacturer and is .1 mfd at 8000 volts.  The original is .1 mfd at
7500 volts according to the manual.  Ted Henry still answered his
phone as of about two years ago when I called him at the number on
their website. He was very helpful and send me a new ,annual for my
3KA.
Dave W7VM

On Mon, Sep 4, 2023 at 12:23 AM John Lyles <jtml at losalamos.com> wrote:
>
> Henry Radio designed their single phase HV power supplies for the 2K and 3K families of amplifiers using a single section L-C filter. But there is a special trick in that the 8Hy series choke is resonated with a shunt capacitor. This cap is critical and it works under stress being in a resonant circuit at 120 hz (100 Hz for 50 Hz powerline version). It creates a notch in the 120 Hz ripple voltage and makes that L look like a high impedance at some load current. All power inductors have some swinging of L as DC current is varying so this resonance is usually chosen to work at the lowest operating current, like idling current without modulation. Or key up for CW.
> When in resonance or just on the high side as DC current through the choke is low (L is highest), the oil/paper capacitor has large circulating current and high peak to peak 120 Hz voltage across it.
>
> As DC current goes up on voice peaks or key down, the critical Lmin is not as important, as the RF load is in parallel with the bleeder. You can read about critical inductance and bleeder resistor selection in HV power supplies having L-input choke in old ARRL or West Coast Radio handbooks, and old Terman textbooks.
>
> Anyone, my point being that is this capacitor has failed or drifted off value, then the 120 Hz ripple will not be attenuated well, at low modulation it may sound like hum, which it is. Replacement of the 16-20 uF filter cap will not affect or suppress this low freq hum if the resonant section is not working. It's job is to attenuate the 240 Hz and higher harmonics, provided stored energy for the peak RF demands, and help regulation of Vloaded/Vunloaded. To really knock down the residual ripple it would need to be much larger.
>
> Mark, i would measure that resonating capacitor first. Be sure to short it out carefully for residual charge. During operation it could also be shorting out the choke if it has failed;  disconnect it for the measurement of both resistance and capacitance. Report back here so we know what you found.
>
> The cap must be carefully selected, so don't just grab any cap as a replacement. Henry was remiss in not explaining the importance of this circuit in their manuals. Resonant choke input filters were clever circuits but failure can be hidden in them, no fireworks and smoke.
>
> Henry, Harris, Heathkit, and Broadcast Electronics all used them in certain amplifier models. I designed the one for Broadcast Electronics in the 1980s, and it was a fun challenge for this young EE at the time, building power electronics. I had luck of finding one of the original choke designers at SNC transformer in Oshkosh, and we spent weeks perfecting the L vs current response to work with microwave oven polypropylene dielectric capacitors as they had around 4kV of AC across them at resonance. Being an FM transmitter, the only requirement was to hold the voltage variation down when the excitation was removed on the class C 4CX3500A PA. I never had a chance to do it for a SSB amplifier though, a more complex design as you don't want to create an unstable wobbly voltage at some audio modulation frequency or keying rate.
>
> 73
> John
> K5PRO
>
> _______________________________________
> Date: Sun, 03 Sep 2023 15:37:41 -0500
> From: r-emails at n5ot.com
> ....
> I have a Henry 2K-4A console, and when I use it on the air, a few people
> have told me my signal is not pure. One described AC hum on both sides
> of my signal frequency. Another friend said I had "sidecars."
>
> My conclusion is I need to replace the big (oil-filled) capacitor in the
> power supply. I have a friend with an older Henry, I think it was a
> 2K-3 console, who had a similar-sounding issue, and he says he changed
> his big capacitor in the power supply, but it didn't really fix the
> problem. He sold the amp and I got the capacitor that didn't fix his
> problem.
>
> Two questions:
> 1. Am I looking in the right direction or the wrong direction? Any
> other PS due diligence I need to do? Any Henry 2K-4A-specific anecdotes
> in the brain trust?
>
> 2. My Henry has the factory capacitor from the 1970s, which is 20uf @
> 5000 volts. The replacement I have says "replacement for Henry
> capacitor" but the values are 16uf @ 7500 volts. It's close to the same
> physical size but not exactly the same size. It has a 2019 date stamp.
>
> Guidance appreciated.
> 73 - Mark N5OT
>
> On Sep 3, 2023, 9:05 PM, at 9:05 PM, amps-request at contesting.com wrote:
> >Send Amps mailing list submissions to
> >       amps at contesting.com
> >
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> >than "Re: Contents of Amps digest..."
> >
> >
> >Today's Topics:
> >
> >   1. Re: Test (Mark Bitterlich)
> >   2. Henry hum on transmitted signal (r-emails at n5ot.com)
> >   3. Re: Henry hum on transmitted signal (Steven Katz)
> >   4. Re: Henry hum on transmitted signal (Mark Bitterlich)
> >   5. Re: Henry hum on transmitted signal (Jim Brown)
> >   6. TL-922 relay source ? (N4IJ)
> >
> >
> >----------------------------------------------------------------------
> >
> >Message: 1
> >Date: Sun, 03 Sep 2023 14:54:04 -0400
> >From: Mark Bitterlich <markbitterlich at embarqmail.com>
> >To: Mark - N5OT <r-emails at n5ot.com>, Amps <amps at contesting.com>
> >Subject: Re: [Amps] Test
> >Message-ID: <TMSMTP03OCvux4Jf7zy0002183f at tmsmtp03oc.mail2world.com>
> >Content-Type: text/plain; charset=utf-8
> >
> >That's three in a row.?If you have hum in your Henry Amplifier it's
> >either because of a flaw in HV filtering, or in the exciter itself.
> >Just my 2 cents.?Best of luck.?De wa3jpy
> >-------- Original message --------From: Mark - N5OT <r-emails at n5ot.com>
> >Date: 9/3/23  6:35 AM  (GMT-05:00) To: Amps <amps at contesting.com>
> >Subject: [Amps] Test Ascii test.? Did it come through?? Amps readers
> >disregard.Good day,73 - Mark
> >N5OT_______________________________________________Amps mailing
> >listAmps at contesting.comhttp://lists.contesting.com/mailman/listinfo/amps
> >
> >------------------------------
> >
> >Message: 2
> >Date: Sun, 03 Sep 2023 15:37:41 -0500
> >From: r-emails at n5ot.com
> >To: amps at contesting.com
> >Subject: [Amps] Henry hum on transmitted signal
> >Message-ID: <55b0c78fa738a3e981ee9997313b0c06 at n5ot.com>
> >Content-Type: text/plain; charset=US-ASCII; format=flowed
> >
> >I see there was no content in my messages the first time around.  I'm
> >not sure what the problem is, but the workaround is to use a different
> >email program.  Here's what I wrote:
> >- - - - - - - - - - - - - - - - -
> >Greetings,
> >
> >I have a Henry 2K-4A console, and when I use it on the air, a few
> >people
> >have told me my signal is not pure.  One described AC hum on both sides
> >
> >of my signal frequency.  Another friend said I had "sidecars."
> >
> >My conclusion is I need to replace the big (oil-filled) capacitor in
> >the
> >power supply.  I have a friend with an older Henry, I think it was a
> >2K-3 console, who had a similar-sounding issue, and he says he changed
> >his big capacitor in the power supply, but it didn't really fix the
> >problem.  He sold the amp and I got the capacitor that didn't fix his
> >problem.
> >
> >Two questions:
> >
> >1. Am I looking in the right direction or the wrong direction?  Any
> >other PS due diligence I need to do?  Any Henry 2K-4A-specific
> >anecdotes
> >in the brain trust?
> >
> >2. My Henry has the factory capacitor from the 1970s, which is 20uf @
> >5000 volts.  The replacement I have says "replacement for Henry
> >capacitor" but the values are 16uf @ 7500 volts.  It's close to the
> >same
> >physical size but not exactly the same size.  It has a 2019 date stamp.
> >
> >Guidance appreciated.
> >
> >73 - Mark N5OT
> >
> >
> >------------------------------
> >
> >Message: 3
> >Date: Sun, 3 Sep 2023 20:47:11 +0000
> >From: Steven Katz <stevek at jmr.com>
> >To: "r-emails at n5ot.com" <r-emails at n5ot.com>, "amps at contesting.com"
> >       <amps at contesting.com>
> >Subject: Re: [Amps] Henry hum on transmitted signal
> >Message-ID:
> >       <BY5PR16MB40020A4B55AC971ACBDB4BE2DAEAA at BY5PR16MB4002.namprd16.prod.outlook.com>
> >
> >Content-Type: text/plain; charset="us-ascii"
> >
> >What does the HV indicate in standby, transmit (no drive, just idling)
> >and key-down at full power?
> >
> >This is key to determining if it's actually a power supply problem.
> >
> >-----Original Message-----
> >From: Amps <amps-bounces at contesting.com> On Behalf Of r-emails at n5ot.com
> >Sent: Sunday, September 3, 2023 3:38 PM
> >To: amps at contesting.com
> >Subject: [Amps] Henry hum on transmitted signal
> >
> >I see there was no content in my messages the first time around.  I'm
> >not sure what the problem is, but the workaround is to use a different
> >email program.  Here's what I wrote:
> >- - - - - - - - - - - - - - - - -
> >Greetings,
> >
> >I have a Henry 2K-4A console, and when I use it on the air, a few
> >people have told me my signal is not pure.  One described AC hum on
> >both sides of my signal frequency.  Another friend said I had
> >"sidecars."
> >
> >My conclusion is I need to replace the big (oil-filled) capacitor in
> >the power supply.  I have a friend with an older Henry, I think it was
> >a
> >2K-3 console, who had a similar-sounding issue, and he says he changed
> >his big capacitor in the power supply, but it didn't really fix the
> >problem.  He sold the amp and I got the capacitor that didn't fix his
> >problem.
> >
> >Two questions:
> >
> >1. Am I looking in the right direction or the wrong direction?  Any
> >other PS due diligence I need to do?  Any Henry 2K-4A-specific
> >anecdotes in the brain trust?
> >
> >2. My Henry has the factory capacitor from the 1970s, which is 20uf @
> >5000 volts.  The replacement I have says "replacement for Henry
> >capacitor" but the values are 16uf @ 7500 volts.  It's close to the
> >same physical size but not exactly the same size.  It has a 2019 date
> >stamp.
> >
> >Guidance appreciated.
> >
> >73 - Mark N5OT
> >_______________________________________________
> >Amps mailing list
> >Amps at contesting.com
> >http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> >------------------------------
> >
> >Message: 4
> >Date: Sun, 03 Sep 2023 17:08:40 -0400
> >From: Mark Bitterlich <markbitterlich at embarqmail.com>
> >To: Amps <amps at contesting.com>
> >Subject: Re: [Amps] Henry hum on transmitted signal
> >Message-ID: <TMSMTP03OCb7NMT665800021b5f at tmsmtp03oc.mail2world.com>
> >Content-Type: text/plain; charset=utf-8
> >
> >
> >Steve Katz mentioned:"What does the HV indicate in standby, transmit
> >(no drive, just idling) and key-down at full power? This is key to
> >determining if it's actually a power supply problem."It is also key in
> >determining if you're experiencing voltage drop at the wall outlet
> >where the amp is plugged in.?IMHO you need to somehow listen to your
> >own signal, so as to listen to it with a pure carrier versus listening
> >to it with modulation.?Yes, a bad filter cap in the power supply can
> >cause this, but so can a florescent light near the microphone wiring,
> >or even a radio sitting directly on top of a 12 volt power supply.?Dive
> >bombing a problem like this can become expensive relying on others to
> >reply to: "Can you hear it now?"??Beg/borrow/build another was to see
> >(scope) or listen to your transmitted signal. This will eminate a lot
> >of "possibilities", and give you a path forward, while learning in the
> >process.?De wa3jpy-------- Original message --------From: Steven Katz
> ><stevek at jmr.com> Date:
> >9/3/23  4:47 PM  (GMT-05:00) To: r-emails at n5ot.com, amps at contesting.com
> >Subject: Re: [Amps] Henry hum on transmitted signal What does the HV
> >indicate in standby, transmit (no drive, just idling) and key-down at
> >full power?This is key to determining if it's actually a power supply
> >problem.-----Original Message-----From: Amps
> ><amps-bounces at contesting.com> On Behalf Of r-emails at n5ot.comSent:
> >Sunday, September 3, 2023 3:38 PMTo: amps at contesting.comSubject: [Amps]
> >Henry hum on transmitted signalI see there was no content in my
> >messages the first time around.? I'm not sure what the problem is, but
> >the workaround is to use a different email program.? Here's what I
> >wrote:- - - - - - - - - - - - - - - - -Greetings,I have a Henry 2K-4A
> >console, and when I use it on the air, a few people have told me my
> >signal is not pure.? One described AC hum on both sides of my signal
> >frequency.? Another friend said I had "sidecars."My conclusion is I
> >need to replace the big (oil-filled) capacitor in the p
> >ower supply.? I have a friend with an older Henry, I think it was a2K-3
> >console, who had a similar-sounding issue, and he says he changed his
> >big capacitor in the power supply, but it didn't really fix the
> >problem.? He sold the amp and I got the capacitor that didn't fix his
> >problem.Two questions:1. Am I looking in the right direction or the
> >wrong direction?? Any other PS due diligence I need to do?? Any Henry
> >2K-4A-specific anecdotes in the brain trust?2. My Henry has the factory
> >capacitor from the 1970s, which is 20uf @5000 volts.? The replacement I
> >have says "replacement for Henry capacitor" but the values are 16uf @
> >7500 volts.? It's close to the same physical size but not exactly the
> >same size.? It has a 2019 date stamp.Guidance appreciated.73 N5OT
> >
> >------------------------------
> >
> >Message: 5
> >Date: Sun, 3 Sep 2023 15:54:30 -0700
> >From: Jim Brown <jim at audiosystemsgroup.com>
> >To: amps at contesting.com
> >Subject: Re: [Amps] Henry hum on transmitted signal
> >Message-ID:
> >       <1a07d039-cf6c-7d9d-3aa9-e1be09b96036 at audiosystemsgroup.com>
> >Content-Type: text/plain; charset=UTF-8; format=flowed
> >
> >On 9/3/2023 1:37 PM, r-emails at n5ot.com wrote:
> >> I see there was no content in my messages the first time around.
> >
> >That happens when you send html. The server for all contesting.com
> >reflectors rejects it, yielding blank emails.
> >
> >73, Jim K9YC
> >
> >
> >
> >------------------------------
> >
> >Message: 6
> >Date: Sun, 3 Sep 2023 23:04:59 -0400
> >From: N4IJ <dougn4ij at gmail.com>
> >To: amps at contesting.com
> >Subject: [Amps] TL-922 relay source ?
> >Message-ID:
> >       <CA+Ht2hN5=UAkRH7Ks-D+_Ly2wLU8PuAjfDU6Xaq_jee0AyRcwA at mail.gmail.com>
> >Content-Type: text/plain; charset="UTF-8"
> >
> >Anyone know if there is a source for the time delay relay for the fan ?
> >
> >If I find one I might swap both relays on the board while there.
> >
> >S51-2403-05    relay
> >S51-2402-05.   relay
> >
> >I found a place that sells a drop in replacement board too. Anyone used
> >one  before ? X54-1300-10CTR
> >
> >Doug N4IJ
> >
> >
> >------------------------------
> >
> >Subject: Digest Footer
> >
> >_______________________________________________
> >Amps mailing list
> >Amps at contesting.com
> >http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> >------------------------------
> >
> >End of Amps Digest, Vol 249, Issue 4
> >************************************
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